Protein trimer

In biochemistry, a protein trimer is a macromolecular complex formed by three, usually non-covalently bound, macromolecules like proteins or nucleic acids. A homotrimer would be formed by three identical molecules. A heterotrimer would be formed by three different macromolecules. Type II Collagen is an example of homotrimeric protein, while Type I collagen is an AAB-type heterotrimeric protein.

Porins usually arrange themselves in membranes as trimers.